Concrete floor slab – random cracking in exposed slab

Cause

Shrinkage cracking if concrete slab is not kept sufficiently wet during the curing process 

Repair

  • two key factors for dealing with cracks in concrete floor slabs are to establish the cause of the cracking and to determine whether the crack is live (getting wider or longer) or is dormant (it is not changing)

  • for very minor shrinkage cracking that is not increasing, and where the appearance/location is acceptable, leaving the floor as-is is an option. (Extremely fine cracking may actually become less visible over time)

  • dormant cracks can be chased and then filled with traditional cement grout or mortar or a specialised epoxy resin or other material

  • where a crack is judged to be live, any material used to fill it must be flexible

  • a specialist concrete floor company, registered building survey or a chartered professional (structural) engineer may be able to provide additional advice

Cause

No or an insufficient number of shrinkage control joints (saw cuts) in the floor slab

Repair

  • as above

Cause

Building movement or ground settlement 

Repair

  • floor slabs can crack as a result of earthquake, ground slumping, or ground movement on certain types of soil, such as clay soils, where there may be seasonal expansion/contraction

  • for very minor shrinkage cracking that is not increasing, and where the appearance/location is acceptable, leaving the floor as-is is an option. (Extremely fine cracking may actually become less visible over time)

  • dormant cracks can be chased and then filled with traditional cement grout or mortar or a specialist epoxy resin or other material

  • where a crack is judged to be live, any material used to fill it must be flexible

  • where a crack is large or getting larger, contact a chartered professional (structural) engineer for advice

  • for cracking that is the result of an earthquake, if you have fire insurance for the property then you automatically have EQC cover – contact EQC